Creative

I going to have to create a tutorial on this but read the help on brushes. 
 
1. create an image  in Affinity 256 x 256 px square
 
2. add a black background
 
3. draw your subject ( in your case the stitch in white)
 
4. export a .png file 
 
5 create a new brush based on your png image
 
6. double click the brush in the tool to envoke the brush editor
 
7. change setting to repeat and adjust the stroke to the size you want ( this sets the default)
 
8. done rename your brush if you like.

I think that would be describes as "text on path" and is on the list of things they aim to incorporate in the future